Spring suspension for vehicles



A. F. HICKMAN 4 sheets-'sheet 1 S ma l INVENTOR o BY @SIMS W .m ATTORNEYS SPRING SUSPENSION Fon VEHICLES original Fiied Fe. 27, 1934 KIR Bmw. uw I S July 21, 1942.

,my 21, 1942. A.; HICKMAN 2,290,183

SPRING SUSPENSION FOR VEHICLES k l 9- 2 a lNvA TER @y wf ATTORNEYS July 2l, 1942. A, F, HlKMAN 2,290,183

' SPRI'NG-sUsPENsIoNFoR vEHlcLEs July 21, 1942- A. F. Hlrc'zxlvuluuY 2,290,183

' V SPRING SUSPENSION FOR YEHIcLl-S Original Filed'Feb. 27, 1934 4 Sheets-Sheet 4 Mww l figur ATTORNEYS Patented July 21, 1942 UNITED sTATEs PATENT OFFICE SPRING SUSPENSION FOR VEHICLES Albert F. Hickman, Eden, N. Y., assignor to Hick-v man Pneumatic Seat Co. Inc., Eden, N. Y., a corporation of New York v Original applications February 27,` 1934, Serial No. 713,161, and January 27, 1940; Serial No. 315,985. Divided and this application July 24, 1940, Serial No. 347,186

1v Claim. (Cl. 280-124) applications Ser. No. 713,161, led February 27,

1934, for Vehicle spring suspension, now Patent No. 2,245,585, dated June 17, 1941, and Ser. No. 315,985, filed January 27, 1940, for Spring suspension for vehicles, now Patent No. 2,246,044, dated June 17', 1941, and is more particularly movement; 11. To prevent any change of steering spindle caster even though the resilient members of the spring suspension are stretched past their elastic limit or become fractured; and, at the same time, to eliminate the need of torque rods; 12. To considerably reduce side sway of the vvehicle even if the axle pivot of the spring suspension is below the component of the sprung weight center of gravity of the companion axle; 13. To prevent the vehicle body from being subjected to lateral shocks as a consequence of lateral axle movement and to thereby also prevent tire scuff; v14. To prevent any of the parts of a spring suspension of this type from becoming directed to the form of the invention shown in Figs. 16 and 17 of said first mentioned copending application Ser. No. 713,161 and as also shown in Figs. 13 and 14 of said second mentioned copending application Ser. No. 315,985, these figures l being reproduced herein ,as Figs. 10 and 1l, re-

spectively.

The subject matter of the invention of this divisional application particularly involves thecombination of the frame, axle, torsion spring assembly and shock absorber, shown in Figs. 10 and 11.

The principal objects of the invention are:

1. To resiliently oppose both up and down vehicle wheel movement by 'a purely geometric l resilient resistance instead of by an arithmetic or a partially arithmetic and partially geometric resilient resista-nce; 2. To reduce vehicle side sway any desired amount down to and including zero side sway, and even beyond to any desired amount of negative side sway; 3.l To eliminate wheel tramp; 4. To considerably reduce the torsional forces to which the vehicle body is subjected. particularly as to the end of the body which is adjacent the axle being deflected; 5. To rapidly dampen out periodic vibration of the spring suspension even if the shock absorbers should become more or less inoperative or even fractured; 6. To reduce the number of shock absorbers required on the vehicle and to reduce the work imposed upon them; 7. To eliminate all frictional resistanceexcept that incident to pivot bearings and shock absorbers; 8. To entirely eliminate the squeaks and lubrication inconvenience of the conventional leaf spring; 9. To definitely limit the stress to which the resilient elements may be subjected; 10. To prevent the wheels fromdragging the body down when said locked in a past-dead-center position; and 15. To

. enable the vehicle to be safely driven even if the resilient members of the spring suspension become fractured. Numerous other objects of the invention and practical solutions thereof are described in detail in the hereinpatent specification wherein:

In the accompanying drawings:

Fig. l is a diminutive, top plan of a passenger automobile chassis, provided with one form of my improved spring suspension. 9

Fig. 2 is a diminutive, vertical, longitudinal vsection thereof, taken on line 2-2, Fig. 1.

Fig. 3 is a fragmentary front end elevation thereof showing the front axle and associated parts.

Figs. 4 and 5 are fragmentary, longitudinal sections thereof, taken on correspondingly numbered lines of Fig. 3.

Fig. 6 is a fragmentary, vertical, longitudinal section through the rear end of the vehiclel chassis, showing the rear axle and its associated parts. ,j

Fig. 7 is a fragmentary, vertical, transverse section thereof, taken on line 1-.1, Fig. 6.

Fig. 8 is a fragmentary, vertical, transverse section thereof, similar to Fig. 7 but taken on a line indicated by 8-8, in Fig. 6 and showing the parts in a different position from that of the other figures.

Fig. 9 is a fragmentary, horizontal section thereof, taken on line 9 9, Fig. 6.

Fig. 10 is a fragmentary end elevation, taken on line I0-|D, Fig. 11 of a modified form of the invention.

Fig; 11 is a fragmentary', vertical, longitudinal section thereof, taken n line ll-I I,Fig. 10.

It is to be understood that similar characters ures of the drawings.

wheels move down beyond their normal range of My invention may be embodied in various forms and in spring suspensions of different constructions, and the present embodiments thereof are to be regarded merely as a few of the set-ups which carry out the inventionin practice.

In the form of the invention shown in Figs. l-9, and in all the other forms of the invention, the main frame of the vehicle chassis is constituted in the usual and well known manner of a pair of longitudinal and substantially horizontal, side frame bars 35 and 30| which are connected at their iront and rear ends respectively by the front and rear cross bars 3| and 3| I.

The entire vehicle chassis, together with its spring suspension, is constructed substantially symmetrically about a vertical longitudinal medial plane, and hence it is deemed sufficient to confine the following description almost entirely to the one (left) side of the vehicle, it being understood that a similar and substantially symmetrical arrangement is to be found on the other (right) side of the vehicle. Furthermore, the spring suspension at the rear end of the construction of Figs. 1 9 is somewhat simpler 'in construction than the front end, and will for that reason be described rst.

Secured adjacent the rear end of the left, side, frame bar 35 is a pair of hangers 32 and 32|). In the lower end of the forward hanger 33 (see Figs. 9, 7 and 6) is journaled a pivot pin 33| having a head and a nut similar in appearance to a bolt. Said pivot pin 33| is shown as arranged generally in line with a universal joint 34 which connects with a torsion rod 33, the extreme forward end of the latter being shown as bent sharply upward to form the torque arm 35. as shown in Figs. 4, 3, 2 and 1. 'I'he upper end of said torque arm is shown as provided with an adjusting screw 36 (or other suitable adjusting means), the inner end ofwhich bears against a pad 3l which may, if desired, be constructed of resilient material such as rubber, and is suitably secured to the adjacent vertical longitudinal face of the companion frame bar 3G. The purpose of this adjustment screw 36 is to adjust the amount of torsional stress imposed upon its companion torsion rod 33.

It is to be understood that when such an adjustment is not desired (if it be desired to render the device more fool-proof, for instance), the spring suspension may be produced with sufiiciently restricted torsional and other tolerances, and said adjusting screw 36 then entirely eliminated. Likewise, the pad 3l may, if desired, be also eliminated, a resilient connection at this point being, as a matter of fact, of very small intrinsic worth due to the fact that only under very unusual circumstances will conditions be such as to allow the torque arm 35 to move away from the frame bar 30. It is likewise obvious that the universal joint 34 may also be eliminated if the vehicle set-up is such as to permit the two sections of the torsion rod 33 to be disposed in axial alignment with each other.

If desired, the intermediate portions of the torsion rod 33 may, as shown, be suitably supported on the frame bar 30 by a pair of bearings 38 and 38| the latter being secured to said frame bars 30, 30| in any suitable manner.

The rear portion or head of the universal joint 34 is suitably flanged and detachably connected by cap screws 4U with the inner end of a bifurcated, front crank arm 4|. Thisl construction, in eiect, rigidly connects the pivot pin 33| with said front crank arm 4|. It is obvious that such e rigid connection may be effected in numerous ways other than in the particular manner illustrated. When the vehicle is normally loaded and at rest, this front crank arm 4| projects outwardly and substantially horizontally from the tor-- sion rod 33, as shown in Figs. '7, 6, 9, 1 and 2; In this position the outer end of said front crank arm 4| is resiliently urged downwardly by the resilient stress imposed upon it by the torsional stress of its companion torsion rod 33.

As best shown in Fig. 9, the outer part of said bifurcated front crank arm 4| is connected on its outer rear side by an integral webbing 42 (or otherwise) with the outer part of a companion, bifurcated, rear crank arm 4|U. The inner end of this rear crank arm 4|() is provided with a pivot pin 43 which is pvoted in the rear hanger 320 aforedescribed. The axis of this pivot pin 43 is coincident with the axis of the pivot pin 33| thereby permitting the two crank arms 4| and 4|@ (together with the integral webbing 42 which joins them) to swing in a vertical transverse plane about the common axis of said pivot pin 33| and of said pivot pin 43.

The outer ends of both of said crank arms 4| and l are bifurcated and are provided with a pair of horizontal pivot pins 44 which are axially in line with each other. The central portion of each pivot pin 44 is pivoted in the normally lower end of a companion link 45, which latter, in the normal or static, loaded position of the vehicle spring suspension shown in Figs. 7, 6, 9 extends upwardly and inwardly from said pivot pin 34.-

The upper ends of the two links 45 are split (see Fig. 7) and are clamped upon the opposite ends or a relatively'long, horizontal, longitudinal, axle-pivot shaft 46. By reason of the fact that said links 45 are both clamped at their upper ends to said axle-pivot shaft 46, the term links is not strictly accurate, but has been here used to avoid excessively clumsy phraseology and to more clearly distinguish said links from the crank 'arms 4|, 4H).

Between said links 45 is disposed an upstanding Y shaped trunnion 41, the upper, bifurcated arms of which are journaled on said axle-pivot shaft 46 while its lower central part or head is suitably secured by welding or otherwise to a companion wheel spindle 48. The latter has a rear, driving wheel 50 journaled thereon in the usual and well known manner. This spindle 48 constitutes one of the outer ends of the rear or drive axle (or axle housing) 5|.

It is admitted that, in ordinary parlance, the outer portion of an automobile drive axle is not ordinarily denominated a spindle, but it is so dened in Websters dictionary and it is necessary to assume some such definition as this if generic claims are to be drawn to cover the various forms of axles and wheel spindles illustrated herein. As far as the present spring suspension invention is concerned, there is no requirement that the driving axle 5| or any of the axles illustrated herein be constructed in one piece, inasmuch as each wheel spindle 48 is provided with its own individual spring suspension. Thence it is deemed properto denominate each end of said drive axle 5| as a wheel spindle.

When said drive axle 5| drops approximately toits lowermost position relatively to the vehicle frame, as shown in Fig. 8, there is a, possibility (unless such a contingency be positively prevented) that the crank arms, 4|, H0 and links 45 will be moved by inertia forces past their deadcenter position, and become locked in this Position. To prevent any such occurrence a at, limiting spring 52 is secured to the central part of the trunnion 41 by means of cap screws 53 or otherwisethe outer portion of said limiting spring 52 being adapted to make contact (see Fig. 8) with the central, outer portion of the webbing 42 which forms an integral part of the two crank arms 4| and 4|0. This contact between said spring 52 and webbing 42 is initially made at -a relatively long distance from the absolute dead-center position and the parts then gently stopped at the iinal position of complete rest shown in Fig. 8 where the parts are shown dead-center position, said parts are not likely to lock in this past-dead-center position because the resilient force of the torsion rod 33 is always urging the pivot pins 44 downwardly, and this factor may, in actual practice, be quite safely relied upon to break any possible dead-center locking.

When the axle 5| is forced upwardly relatively to the main frame from the position of Fig. 7 (or, vice versa, when the body under the inuence of momentum, is forced downwardly relatively to said axle) the effective resilient opposing force of the torsion rod 33 increases at a geometric and not at an arithmetic rate. In this particular case, the geometric rate is of the accelerated increase type, in which increments of vertical movements of the axle are opposed by an accelerated rate of resilient resistance. This is primarily due to the progressive decrease in the eiective lever arm of the crank arms 4 l, M0, as they swing upwardly and inwardly about the rear section of the torsion rod 33 and the pivot pin 43 as an axis of rotation. This action is also inuenced by the varying angularity of the links 45 and the fact that increments of vertical displacement of the pivot pins 44 cause accelerated rates 0f in-crease in the angular displacement of the torsion rod. 33. This latter is due to the fact that increments of vertical movement of said pivot pins 44 are not proportional to the accompanying increments of angular twist to which their companion torsion rod 33 is subjected.

This geometric action also occurs when the axle 5| moves downwardly a certain distance relatively to the :frame bar 30 from the normal position olf Fig. 7 to a position intermediate of the extreme position of Fig. 8. Throughout this particular movement, the geometric action is of the accelerated decrease type, i. e., as the axle passes through increments of downward movement, the rate of decrease of the resilient force tending to push said axle downward increases.

Thus, as the axle moves downwardly yfrom the position of Fig. '7, the resilient force tending to push it downwardly decreases at an accelerated rate. Finally,4 at a position intermediate of Figs. 7 and 8, this downward pressure on the axle 5| becomes equal to zero. Then, as said axle continues to move downwardly beyond this intermediate point, thetorque arm 35 is turned or rotated outwardly away from its pad 31, thereby relieving the torsion rod 33 of all torsional stress, thereby maintaining at zero the value of the resilient force interposedbetween the axle and the main frame. This condition continues .until the axle has moved downwardly to its low. ermost position as shown in Fig. -8. During this last mentioned downward axle movement, said axle, together with its wheels 50 and other vertical forces are concerned, said vehicle frame is, at this time, free to float along solely under the influence of gravity (plus whatever momentum forces are present), this feature of the invention being of particular significance when it is realized that the load carried by the vehicle is also, rat this time, 'solely under the inuence of gravity (plus whatever vertical momentum forces are present). The consequence is that, within this particular range of movement, the load in the vehicle moves vertically up and down with the same acceleration and deceleration as the .body and hence without changing the pressure between the load and body. Such a desirable result is quite different from that obtained .from the conventional spring suspension in which the axle and the rest of the unsprun-g weight drags or jerks down the main frame whenever the strain imposed on the main springs is negative. In the present invention no such negativeforce, tending to pull the body downward, is possible.

The front or steering axle 5|| of the vehicle of Figs. 1-9 is provided with a spring suspension analogous to that just described for the back axle 5|. However, certain inherent characteristics of a [front axle require certain modcations to the present invention when the same is to be applied to a front axle. In the case of the form of front axle 5|| shown in Figs. 3, 4, 5, 1 and 2, for instance, a wheelspindle 48| having a wheel 50| journaled thereon is pivoted on a substantially vertical spindle pin 55 at each end of said front axle 5| The two wheel spindles 48| at opposite ends of said axle are assumed to be cross connected for steering purposes in the usual and well known manner.v Extending horizontally inward from one of these spindles is a steering arm 56 connected by a universal joint 51 with the front end of the usual steering or drag link 58 (see Fig. 5). The rear end of the latter is connected, in the usual and well known manner, by a universal joint 60 with the lower end of a manually actuated steering lever 6|.

It is important that the steering arm 56 be never moved relatively to the axle 5|! as a consequence of any sort of up and down axle movement. Any suchdeleterious movement has lbeen absolutely prevented by thev construction hereV illustrated. A radius rod 62 is connected at its front end by a universal joint 63 with the front axle 5|I and is connected at its rear end by a universal point 64 with the side frame bar 30 of the main frame. This radius rod 62 has its universal joint pivots 63 and 54 spaced apart the same distance as the spacing apart of the uniitstrunnion 41| is free to slide a short distance longitudinally on the axle pivot shaft 46|, the latter being firmly clamped at its opposite ends in the upper split ends of theA links 45|; Be-

Q- mi cause of this arrangement, as the axle 5|| rises or falls, it is caused to move longitudinally about the pivot 64 as a center and to thereby prevent any turning of the spindle 48| about its vertical pivot 55 as the pivot 5l of said spindle swings about the drag link pivot 60 as a center. In actual practice the amount of thislongitudinal movement off the front axle is so small, that both the radius rod 62 and clearance 65 :may be entirely eliminated without any serious detrimental eiect on the steering of the vehicle.

There is one very important factor involved, in any front axle set up, namely the permanence of the caster or the angle in a vertical longitudinal plane of the spindle pivots 55. It is to be noted that, in the present invention, the caster of the steering wheels remainsabsolutely iixed, irrespective of whether or not a radius rod 62 is used and irrespective of whether the torsion rod 33 becomes either deformed or even completely broken.

This feature of xed caster angle is also of some importance with respect to the back axle, where it ensures the permanency of the arcs through which the universal joints. of the propeller shaft are caused to swing as the axle rises and falls. In the case of both front and rear axles, the construction whereby the caster angle is permanently maintained, irrespective of what may happenr to the resilient portionsof the spring suspension, also ensures that all torque imposed upon the axles by the brakes is suitably taken care of without the need of any special torque rods for this purpose.

In the case of both the frontI and the rear axle spring suspensions, the links 45, 45| incline down- Wardly and outwardly. This arrangement has two distinct advantages. One effect of this angular linkage arrangement is that it causes each end of the body of the vehicle to always tend to centralize itself relatively to the companion axle 5| or 5|| as the case may be. This centralizing tendency is caused by the effect of gravity, which may be considered a resilient, downwardly-acting force acting between the body and the roadbed and operating in a manner identical in. its effects to a metal spring connecting said body and the roadbed. It is to be distinctly understood that this force tending to centralize each end of the body is of a resilient nature. Because of this fact the body of the vehicle is not subjected to directly connected lateral forces as a consequence of a lateral axle movement. Such a lateral axle movement-occurs, for instance, when one end only of the axle is raised or depressed and thereby causes horizontal, lateralmovement components in all parts of the axle except at its momentary axis of rotation in those particular cases where said axis lies within the overall length of said axle. In the conventional spring suspension, all movements of the axle which are lateral with respect to the vehicle as a whole are transmitted directly to the body. Because ofthe relatively large inertia of the latter, no appreciable lateral body movement actually occurs when such a conventional vehicle is traveling at high speeds and one end of the axle moves up or down. What does occur is that said body is subjected to a sharp lateral rap of considerable force every time the axle moves in any manner other than translationally. This not only seriously impairs the riding qualtities of the vehicle but also subjects the body to a succession of forces which in a short period of time loosen al1 the body bolts and other such fastenings and cause the whole body to rattle. Another important advantage obtained by the angular arrangement of the links 45, 45| is that it absolutely eliminates wheel tramp. This latter may be broadly defined as a periodic vibration of either axle in a vertical transverse plane. the definition being usually limited to a rotary movement about an axis of rotation located at some point in the axle. In general it may be said that, if one wheel is lifted, and if this movement causes a downward thrust on the opposite wheel, then wheel tramp results. Such wheel tramp is prevented in the present invention by ensuring that the downward thrust of the axle pivot Gt or 48|, as the case may be, lies approximately in a plane intersecting the contact of the tire with the road. When such a condition obtains, a vertical upward thrust against one wheel is opposed by a directly opposite force passing through the axle pivot 46 or 46| and hence no downward thrust is imposed upon the opposite wheel as occurs in the conventional spring suspension.

Another very important; advantage of the present invention is that all forces tending to twist the frame have been very markedly reduced as compared with conventional spring suspensions.

Frame twist may be dened as a torque force4 applied to one end of the frame, diierent in direction and intensity from the torque force imposed upon the other end of the frame. In the present invention, when, for instance, one of the vehicle wheels is thrust upwardly, the frame hangers 32, 320 (or 32|, 32|0) are subjected toA a force intersecting the axis of the pivot pin 43 \(and adjacent short end of the companion torsion rod 33). Such a force constitutes a torque force imposed upon the adjacent end of the vehicle frame, and this, all by itself, would, of course, cause frame twist. It is to be noted, however, that, at this time, the companion torsion rod 33 is under increased stress by reason of the wheel thrust in question and hence the torque arm 35 is subjected to an increased force which also constitutes a torque force upon the vehicle frame. It is to be noted that this increased force which is imposed upon said torque arm 35 is located at one end of the vehicle while the torque force at the pivot pin 43 is at the other end of the vehicle. Furthermore, the forces are not greatly different in intensity or direction. The result of this condition of affairs is that both ends of the vehicle are subjected to torque forces ,which do not differ from each other to any marked degree in either direction or intensity, and hence frame twist is very considerably reduced. In other words, when a certain wheel of the vehicle is forced upward, instead of twisting the one end of the vehicle frame as in the conventional spring suspension the present invention provides that the entire one side of the vehicle will be lifted a minute distance, thereby increasing the inertia resistance of the spring weight to the resilient forces caused by the wheel movement, and very markedly decreasing frame twist and its concomitant twisting and rocking of the body and resulting loosening of the various body fittings.

As to this matter of frame twist, it is to be noted that satisfactory results can only be obtained if the dead end of the torsion rod extends toward the opposite end of the vehicle and is positioned beyond the center of gravity of the car. If this condition does not obtain. then *both ends of the torsion rod cause torque forces which act in the` same general direction and upon the same end of the vehicle and hence cause frame twist. If, as in the present invention, the "dead end of the torsion rod is situated beyond the center of gravity of the sprung weight (body) then the forces are acting upon opposite ends of the vehicle and frame twist is reduced.

It is also to be noted on the present invention that the means whereby resilience is effected does not involve any frictional resistance such as occurs in the case of a conventional leaf spring, and hence is free and non-energy absorbing in its action. Also, having no frictional resistance (except bearings which aiord no particularly difilcult lubrication problems) it does not vary'because of change of frictional resistance as in the l case of the conventional leaf spring.

No shock absorbers are .illustrated in the form of the .invention shown in Figs. 1-9. vHowever, it is desirable to employ shock absorbers in connection with this suspension. Nevertheless the riding qualities of a vehicle equipped with the present invention are not seriously reduced even if the shock absorbers become inoperative or are left off altogether. This is in sharp contrast to the ordinary individually sprung wheel suspension using helical springs, in which case the vehicle receives a terrific wracking and pounding if the shock absorbers become even partially in; operative. In the present invention, it has been found by definite test, that the periodic vibrations of the spring suspension are very rapidly damped out, even in the total absence of shock absorbers. As an example o f how marked the dampening action is, a series of tests were run on three types of spring suspension in which the be the same at both ends of the vehicle because otherwise the frame is subjected to twisting forces whenever any side sway occurs.

0n this basis, we will now consider the side c sway at the front of the vehicle with the spring suspension in normal position as in Fig. 3. If the frontv center-of-gravity component lies on the -the center-of-gravity component is above the load and displacement were the same and also the maximum metal stress in the respective resilient members. It was found that a helical spring, under these circumstances, would come to rest after 800 vibrations-the leaf spring after 20 vibrations-and the present invention after 5 vibrations. Why the leaf spring should be so superior to the helical spring is easyto understand because of the relatively'high friction in a leaf spring even when well lubricated. The signincant cast is that in applicants spring suspension, there is no suchleaf spring friction and yet its performance is four times as good as the leaf spring set-up, despite the fact that the friction resistance of the present invention is not materially different from that of the helical spring, individually sprung wheel set up.

In the present invention, side sway of the vehicle frame can be reduced to any desired extentl including zero side sway and even negative side sway. To deal rationally with this question it is highly desirable that we first mathematically split the center of gravity of thecar into two components, each component lying in the intersection of a vertical, longitudinal, medial, plane with vertical, transverse planes passing through the axes of the companion pair of wheels. Each component of the center of gravity is then the mass which, when the' vehicle is steered to the right or left, creates a lateral force which tends to tip its companion end of the vehicle in a lateral direction relatively of the companion. The reason why nit is desirable to d eal with a center-of-gravity component over each axle individually is because the component over the front axle is usually at a different height above the ground from the center-of-gravity component over the rear axle and hence requires -a different arrangement to obtain the same kind and degree of side sway. 'I'his side sway should line d the resulting side sway will be positive as in the conventional spring suspension.

If, Von the other hand, the center-of-gravity component is situated below the line d, as for instance, on line e, then the side sway is negative. Obviously the amount of such negative side sway is proportional to the distance between the lines i and e. One important feature of the negative Side sway is that, when rounding a corner, the V.center of gravity is shifted toward the inside of the curve and hence lessens the possibility ofthe car turning over. Another distinct advantage ,of negative side sway is that the tendency of the person or goods in the vehicle to move sidewise imder the influence of centrifugal force is lessened. This is because the supporting surface is `tilted when the side sway occurs and hence one component of the side sway force is directed perpendicularly downward against said supporting surface. Negative side sway has the further advantage of being much superior as to its psychological reaction on the persons riding inthe vehicle as compared with zero or positive side sway, not only because of the decrease in the 'gforce tending to move the persons sidewise in their seats, but also becausepthere is a natural tendency for a person to lean inward (or bank) on a curve. '.This psychological effect is probably chiefly due to the instinctive feeling of greater safety which is obtained when the center of gravity is shifted toward the inside of the curve along which the person is moving.

It is obvious'that the amount of side sway varies with the position of the axle pivots relatively to the vehicle frame. When it is desired to keep the maximum possible side sway under any certain definite amount, Athis may be affected by either positioning the axle pivot high enough above the axle to accomplish this result, or kby suitably lowering the center of gravity of the body. It is to be noted in this connection, however, that the factors aiecting side sway change very considerably when the frame and axle are opproximately in the extreme position of Fig. 8. This is due to the fact that, when the parts are approximately in this position, any outward centrifugal movement of the inner part of the vehicle frame, tends to cause the pivots 43, 44 and 46 to all lie in one straight line, and such a dead center tendency is resisted by forces which rapidly approach innity as said pivots approach a straight line relationship. It should be borne in mind, however, that any such condition as that shown in Fig. 8 would be exceeding rare in actual practice, particularly when the vehicle is equipped with shock absorbers whose chief function is to restrain upward movements of the body relatively to the axle.

It has also been found in the present invention from actual practice and from analysis based on said practice that side sway has been rendered mathematically more negative in amount by reason of the angularity of the links 45 which normally slope down and out from the axle pivots 46|. Because of this angularity, when the body shifts laterally lin rounding a curve, the outer part of the body is elevated and the inner part allowed to fall, relativelyto the axles. Such a tilting is equivalent in its effect to lowering the center of gravity of the body or elevating the axle pivots 4.6i, either of these changes rendering sidev sway more negative.

The construction shown in Figs'. 10 and 1l illustrates a modified means of compensating for brake torque and horizontal axle thrust, the modification illustrated in these gures, in particular, the combination of the frame, axle, torsion spring assembly and shock absorber, forming the subject of the present divisional application. In this case the crank arm 4I5 and link 455 are used only to carry the vertical load. All brake torque and other similar forces are carried bya two armed torque rod or Wishbone 85, 850 whichv is connected at its rear end by a universal joint 86 with the crank case 81 of the motor 95 (or otherwise connected with the vehicle frame 305). and has the front ends of its two arms 85, 850 pivoted to the axle 5i5 by the substantially vertical pins 9|. y

By reason of the connection of said'axle with the frame by said torque rod 85, it is no't feasible to rigidly connect the pivot pin 465 with the wheel spindle 485. Hence a swinging bracket 415 been provided, its upper end carrying said pivot pin 465 while its lower end is suitably pivoted on a rocking pin 82 suitably journaled in a bearing box 93 which is 'secured tothe spindle 485, the axis-of rotation of said swinging bracket 415 relatively to said spindle 485 being substantially horizontal and transverse of the vehicle.

It is obvious that such a swinging bracket 415 can be made much lighter in weight for a given height than can the trunnion 41 of Figs. 1-9, and hence such a swinging bracket construction is particularly adapted to be used when, to obtain a large amount of negative side sway, it is desired to have the pivot pin 465 disposed at a considerable elevation relative to the main frame 305 of the vehicle.. This vertical position of said pivot pin 465, as has been previously described,

` has a direct relationship on the amount of side sway to which the main frame 305 of the vehicle is subjected relatively to the axle 515 when the vehicle is rounding a curve, the higher this pivot pin 466 being, the less the resultant side away. It is admitted, on the other hand, that the construction of Figs. 10 and 11 does not provide a fixed castor angle for the wheel spindles 485. However, a passenger automobileconstructed in this manner has been given exceedingly rigorous tests and has shown very remarkable riding qualities.

Actual tests have also shown that a shock absorber, arranged as in these Figs. 10 and il, gives very good results as to riding quality. In this case the shock absorber 94 is directly connected between the frame 305 and the central part of its companion axle, in this case the front axle SI5. The shock absorber illustrated is of the plain, direct-acting, hydraulic plunger type and is connected at its upper and lower ends respectively by resilient ball and socket joints S5 and 96 with the frame and axle. In the present invention a shock absorber has, as one of its chief functions, the preventing of pitching. The placing of the shock absorber 94 at the center of the axle provides for a maximum absorption of' pitching tendencies without materially aiecting the action of one of the axle relatively to the other. This is because when both ends of the axle either rise or fall (as occurs in pitching) the shock absorber o'perates to its maximum capacity because its movement is then the same as that of each of the wheel spindles 485. When, however, one end only of the axle rises or falls relatively to the other end of the' axle, then the resistance to such a movement by said shock absorber is approximately only half of what it would have been if both ends of the axle had been moved a similar amount.

Heretofore it has been common practice to place a shock absorber at each end of each axle so as to reduce side sway in addition to reducing the pitching action. In the present invention side sway has not only been completely eliminated but a step-further made and negative side sway introduced. This releases the shock absorbers from the necessity of cutting down on the normal positive side sway and enables them to function at maximum eiiiciency in the absorption of pitching vby being placed at the center of the axles.

This has the further advantage of reducing frame twist by reason of the fact that all shock absorber pressures are imposed directly upon the medial line of the vehicle, thereby merely tendingv to lift or raise the same bodily (against the full force of its inertia) as compared to the twisting action which occurs when the shock absorber forces are imposed upon only the one corner of the vehicle.

. The conventional shock absorber at each end of the axle also has the function of restraining periodic vertical vibration, but such restraining power is of very incidental importance in the present invention because such vertical vibra- Ations are quickly damped out by its inherent construction and action, as has been previously described. This damping action is so pronounced that the vehicle has fairly good riding qualities even when the shock absorbers become totally inoperative. This is in sharp contrast to the disastrous results which occur when any one of the shock absorbers of an ordinary knee-action spring suspension fails to function.

I claimA as my invention:

A vehicle spring suspension for connecting the frame and axle of a vehicle and comprising: a crank arm pivoted longitudinally on said frame; said crank arm having a pivot at its outer part; an axle pivot connected to said axle; means pivoted at its upper end'on said axle pivot and at its lower end on said crank arm pivot and permitting movement of said axle laterally with reference to said frame, said means extending upwardly and inwardly from said crank arm pivot when said crank arm is in a horizontal position; means resiliently resisting vertical axle movement relative to said frame; and shock absorbing means connecting the Central part of said axle with said frame.

ALBERT F. HICKMAN. 

